1. Field of Invention
This invention relates to a novel (-)-optically active piperazine derivative and a cerebral cirulationimproving agent containing the piperazine derivative as an active ingredient.
2. Description of Prior Art
U.S. Pat. No. 4,528,194 describes that piperazine derivatives of the formula: ##STR2## wherein R.sup.1 is hydrogen or a lower alkyl group, R.sup.2 is hydroxyl, an aralkyloxy group, a lower alkoxy group or a lower alkenyloxy group, R.sup.3 is hydrogen, an aralkyloxy group, a lower alkoxy group, or a lower alkenyloxy group, and R.sup.4 is hydrogen or a lower alkoxy group and pharamceutically acceptalbe salt thereof are effective to selectively vasodilate peripheral vessels, particularly vertebrae, in increasing blood flow and suppressing platelet coagulation and therefore effectively useful as cerebral cirulation-improving agents.